Aqua Sacs are a species of aquatic flora found within the watery environs of Tallon IV, although Samus Aran only encountered them in the recently crashed Orpheon, indicating that they are a rapidly invasive species (the Orpheon had only been there mere hours when Samus discovered Aqua Sacs already growing in relative abundance inside of it). They are the evolutionary counterparts to the Sap Sacs, and may be of a similar and likely related species. They exhibit a bluish sap, possibly indicating the presence of copper, although this is only speculation as no known study has been done into the matter.

Unlike the aforementioned Sap Sacs, the Aqua Sacs utilize small sacs clustered together to achieve the same desired explosive effect, which like their cousins is used as an extreme defensive measure. However, due to the nature of the pressure that water causes on things such as explosions, this procedure is less violent and harmful in nature. When hit with conventional weaponry, the small sac clusters will seem to simply separate and float away from one another, and is not known to cause harm to any known sapient beings. This may indicate that their defense is utilized strictly on much smaller organisms which may be more susceptible to the effect.

As Samus discovered on her mission to the planet, Aqua Sacs are capable of very quickly take hold in new locations, maturing within mere hours, as they had taken root within the Space Pirate frigate Orpheon after it crash landed.